Electrical fuse plug



Dec. 25, 1923. 1,478,752

c. s. MALLETT ET AL ELECTRICAL FUSE PLUG Filed Sent. 17 1921 INVENTORS.

CHARLE 5. MALLETT.

OSCAR E. FORREST.

Patented Dec. 25, 1923.

UNITED STATES PATENT OFFICE.

CHARLES STANLEY MALLETT, OSCAR EDMUND FORREST, AND DAVID MONIE, OF TO- RONTO, ONTARIO, CANADA, ASSIGNORS TO THE CANADIAN GENERAL ELECTRIC CO.

LTD., OF TORONTO, ONTARIO, CANADA, A CORPORATION OF DOMINION OF CANADA.

ELECTRICAL FUSE PLUG.

Application filed September 17, 1921. Serial 1T0. 501,433.

. To all whom it may concern:

Be it known that we, CHARLES STANLEY MALLn'r'r, OSCAR EDMUND FORREST, and DAVID Moms, all of the city of Toronto, in the county of York, in the Province of Ontario, Canada, have invented certain new and useful Improvements in Electrical Fuse Plugs, of which the following is the specification.

Our invention relates to improvements in metal fuse plugs and the object of the invention is to devise a plug which will meet all the standard tests to which a fuse plug is required to be put. This object being carried out:

First: By providing a metal shell, the bottom of which is sealed against the outlet of gases produced by the explosion of the Iuse.

Second: By providing a fuse strip which is so formed as to prevent the electric are continuing in an upward path towards the cap or" the fuse plug and to cause a cushioning efi'ect on the proportionately larger volume of air above the fuse strip in the interior of the fuse plug, thereby preventing a strain on the interior parts of the plug.

Third: By providing means incorporated in the cap for providing an outlet for the gases generated by the explosion and for cooling such gases during their outward passage throughthe outlet and it consists essentially of the constructionand arrangement of parts as hereinafter more particularly explained.

36 Fig. 1 is a cross sectional view of our fuse plug. Fig. 2 is a top plan view. Fig. 3 is a plan sectional view taken through the gas outlet passages and Fig. 4 is an enlarged sectional detail showing the construction of our gas outlet.

In the drawing like characters of reference indicate corresponding parts in each figure.

1 indicates the metal shell of our plug which is provided with the usual thread 2 for the insertion of the plug in a cutout and with an annular bead 3 in proximity to its upper end for a purpose which will hereinafter appear. 4 indicates a central orifice which is located in the lower end or bottom of the shell 2. 5 is a groove which is formed in the bottom Of the shell preferably by stamping up the metal. 6 is a washer formed of. insulating material such as fibre. The

washer 6 is placed against the lower end of the shell so that its orifice is in line with the central orifice 4 of the shell bottom and extends outward so as to cover the groove 5 thereby forming a continuous chamber.

7 is a disc also formed of insulating material which fits within the interior of the shell 1 against the inner face of the bottom, the outer portion resting upon the metal, forming the groove 5. The central portion is depressed or dished downward so as to pass through the orifice 4 and rest against the upper face of the inner portion of the washer 6, thereby dispensing with the necessity of an intervening washer to take up the space between the discs 7 and 6 produced by the formation of the groove 5. The disc 7 is provided with a central orifice in a line with the central orifice of the washer 6. 8 is a rivet which is preferably tubular, the head 9 of the rivet fitting against the outer face of the disc 10. The inner edge of the rivet 8 is turned outward over the edge of the central orifice of the disc 7 thereby securely connecting the discs 6 and 7 together. Although we have shown the rivet 8 as a tubular rivet it may be of any other desired form. such as a split rivet.

11 is a fuse strip which is secured at its lower end to the rivet 8 by soldering or any other suitable means. The opposite end of the strip is bent downward so that the strip is in the form of a loop, the upper end of the loop being located substantially central of the height of the interior of the fuse plug.

The opposite end or that end of the strip which is ordinarily the upper end being secured to the lower portion of the shell 1. 12 is a sleeve of insulating material such as paper or fibre. The sleeve 12 fits within the shell 1 so as to rest at its lower ed e upon the disc 7 extending at its u per en to the top of the shell, the upper e ge of the sleeve being turned inward as indicated at 13.

14 is an insulating collar which surrounds the shell 1 and rests u on the shoulder 3. 15 is an annularring 0 insulating material which also surrounds the upper end of the shell 1, and rests upon the collar 14. 16 is a disc of mica or other suitable material which rests upon the upper edge of the shell 1, such upper edge being turned over the inner edge of the annular ring 15. The disc 16 is provided with a series of perforations 17 which are preferably seven in number. 18 is a cap of our fuse plug. The cap 18 is provided with a central orifice 19, the outer edge being turned downward and carried around the outer edge of the annular member 15 and inward at 20 in the usual manner to secure the cap in position.

21 is a groove which is pressed or embossed in the cap, the inner edge portion 22 of the groove bearing upon the mica disc 16 at the inside of the perforations 17. The groove 21 is located centrally over the perforations 17 so that the gases discharged through such perforations stripe the centre portion of the groove to be deflected in opposite directions. 23 are a serie of radial outlets formed in the cap so that an outlet opening 24 is formed through which the gases are discharged. lt will be noticed on referring particularly to Figs. 2 and 3 that the outlets 23 diiler in number to the number of perforations 17, the number of these outlets is preferably 8. By this means, when the disc 16 is placed within the cap 18 in assembling the parts only one of the perforations 17 can ever come directly opposite one of the outlets 23, thi construction being provided for a purpose which will hereinafter appear.

When an explosion takes place due to the fuse strip 11 being overloaded the hot gases generated thereby tend to pass beneath the lower end of the sleeve 12' and percolate through the crevice formed between the disc 7 and the bottom of the shell and.

through the orifice l of the shell and then radially outward between the bottom of the shell and the disc 6. Any gases which pass through the bottom of the shell in this way 7 are received in the chamber 5 and are held there o as to expand and cool preventing them from passing completely through the bottom of the shell.

Also when the explosion takes place by forming our fuse strip 11 in the form of a loop, the extremity of the loop being located intermediately of the height of the interior oi? the shell prevents the electric are from continuing in a path upwards towards the cap of the fuse plug, such are is instead directed downwards and the surrounding air in the interior of the shell produces a cushioning effect preventing the explosion of the gases exerting great strain upon the upper portion or the interior of the plug to detrimentally effect the same.

And also upon the explosion of the gases the hot gases pass up through the periorations 17 into the groove 21. The gase are carried upward against the base oil the roove being deflected in either direction as indicated by arrow in Fig. 4. As before stated only one of the perforations 17 is directly opposite the outlet 24 the other periterations being more or less to one side of a corresponding outlet. lt will thus be seen nevavaa that the gases received within the groove All are also deileoted more or less to pass iii an annular direction to an outlet. By carrying the gases through the perforations 1'? so that they impinge upon the inner face or the cool urface forming the groove 21 of the cap this contact serves to cool such gases before they reach their outlet to a. sufilcient extent to prevent the gases igniting cotton batting laid. over the plug. The size of the perforations 17 formed in the mica must be large enough to allow of considerable escape of gas to relieve the pressure on the cap and yet be small enough to reduce the dame in the gas to a minimum.

lln plugs imilar to the type above de" scribed and in which means have been provided for permitting of the outlet of the hot gases through the bottom of the plug in such a manner as to allow the gases to escape freely without blowing off the cap, the explosion is so severe that it will destroy the cutout block in which the plug is'screwed, and that the heated gases will maintain an eleotricarc in such a manner as to utterly destroy the cutout block.

By our device when the explosion talres place the hotgases are prevented pmsing through the bottom of the shell, the groove 5 forming the chamber providing a barrier preventing the gas passing to the exterior of the shell. lt Wlll therefore be seen that all the gases discharged from the plug pass upward through the perforations 1 into the groove 21 wherein the major portion of the gases are deflected suilicienrtly against the cool surface to reduce their temperature suiiiciently before they are discharged to prevent ignition of any material with which they may come in contact.

In conclusion, we having an intimate knowledge of the manufacture of fuse plugs and having observed the continual failure of certain similar designed fuse plugs to coinply with all the tests demanded by The llnderwriters Laboratories at Chicago and elsewhere, have devised a plug such as above set forth which will meet all. the inspection Bil llli

laboratorys tests to which a fuse plug may i be required to be put. The object which has been attained by our plug has never arrived at before in any other fuse plug oi similar design in use.

What we claim as our invention is:

1. In a fuse plug, a shell having a central opening in the bottom, a disc secured to bottom of the shell, a groove formed in the shell bottom "forming together with the closure a continuous chamber about the centre of the plug.

2. ln a fuse plug, a shell provided with a central opening, a continuous groove formed in the bottom of the shell concentric to such opening, a closure for such central opening extending over the groove to term a con= llld tinuous chamber, a disc located within the shell and bearing upon the wall of the groove having a central portion depressed through the central opening in the shell against the underlying washer, and means for connecting the disc and washer together.

3. In a fuse plug, a shell provided with a central opening, a continuous groove formed in the bottom of the shell about such opening, a closure for such central opening extending over the groove to form a continuous chamber, a disc located within the shell and bearing upon the wall of the groove and having the central portion depressed through the central opening in the shell against the underlying washer, and a central rivet extending throu h the central opening of the shell and t rough the disc and washer to'connect them together.

4. In a fuse plug, the combination with the shell of the plug, and a gas tight closure for the lower end thereof, of a cap secured to the shell, a gas receiving chamber formed in the cap, gas discharge passages extending from such chamber, and means for directing the gases so as to impinge against the wall of such chamber to be diverted in their course to the discharge passages.

5. In a fuse plug, thecombination' with the shell of the plug, of a disc extending over the open upper end of the shell provided with perforations, a cap secured to the shell and chambered over such erforations, and outlets leading from suc chambered portions.

6. In a fuse plug, the combination with the shell of the plug, of a disc extending over the open upper end of the shell, and provided with a series of perforations, a cap secured to the shell provided with a a chamber extending over the perforations,

and gas outlets extending from such chambers 7, In a fuse plug, the combination with' a shell, a disc extending over the open upper end of the shell and having a series of perforations, a cap secured to the shell, a chamber formed in the cap and extending to the perforations and gas outlets also formed in the cap and leading radially from such groove.

8. In a fuse plug, the combination with shell of the plug, a disc extending over the open upper end of the shell having a series of perforations formed therein, a cap secured to the shell having a groove and a series of radial gas outlets formed in the cap.

9. In a fuse plug, the combination with a shell, of a disc extending over the open upper end of the shell provided with a series of perforations, a cap secured to the shell provided with a chamber extending over the aforesaid perforations, and discharge passages extending from the cham-' ber differentiating in number to the number of perforations.

10. In a fuse plug, the combination with a shell, a disc extending over the open upper end of the shell having a series of perforations formed therein of such a size as to relieve the pressure upon the cap yet small enough to reduce the flame in the gas to a minimum, a cap secured to the shell, a chamber formed in the cap and extending over the perforations to form a gas receiving chamber and gas outlets extending therefrom.

11. In a fuse plug, the combination with ashell, of a disc extending over the shell having a series of perforations, a cap secured to the shell having a groove extending over the perforations and gas outlets leading from such groove.

CHARLES STANLEY MALLETT. OSCAR EDMUND ronmzsr. DAVID MONIE. K 

